T helper 2 Inflammation &Severe Muscularization of Arteries in the Lungs Project Summary / Abstract Pulmonary arterial remodeling, characterized by severe muscularization, is commonly seen in infections with helminth parasites that spend part of their life cycle in the pulmonary artery (e.g. Dirofilaria immitis). These parasites induce a T helper 2 (Th2) response. This same type of lesion is also seen in the bronchial artery in asthma, another Th2-response associated disease, particularly in individuals with asthma of long duration, or in asthmatic cigarette smokers. These associations indicate that severe muscularization of the pulmonary or bronchial arteries might be a consequence of a Th2 driven inflammation. Classically, severe pulmonary arterial muscularization has been described in pulmonary arterial hypertension (PAH). An immune-pathology has been suspected in PAH associated with autoimmune diseases such as systemic scleroderma, viral, or parasitic diseases. In preliminary experiments, we have shown that the Th2 response to soluble antigen alone is sufficient to induce severe pulmonary arterial muscularization and increased right ventricular systolic pressures following acute hypoxia. This was induced in immunized C57BL/6 mice that were given intermittent airway challenges over a prolonged period of time with either of two different antigens. CD4+ T cells and Interleukin (IL)-4 were necessary for the development of pulmonary arterial muscularization and transient depletion of an important Th2 cytokine, IL-13, decreased the severity of the lesion. IL-13 alone was not sufficient indicating that a complex Th2 - initiated process induced severe arterial muscularization. Which components of the Th2 response directly cause the arterial muscularization and how the Th2 response components interact are important questions yet to be answered. To address these questions, three specific aims are proposed to identify the roles of T cells and dendritic cells (DCs) and soluble immune mediators (IL-17, IL-33) for the effector phase during which arterial muscularization occurs. Experiments are proposed to deplete or to adoptively transfer T cells, dendritic cells, and soluble immune mediators during the time periods that arterial injury and remodeling occur in the lungs. Using techniques that are securely established in my laboratory, the hypothesis to be tested is that T cells and DCs control the production of IL-17 and IL-33 thereby directly determining the degree of pulmonary arterial muscularization and right ventricular function. The long range goal of this work takes advantage of the mouse model developed in my laboratory to identify targets for the diagnosis, prognosis and management for inflammation associated PAH, such as PAH seen in scleroderma patients. This is unique and significant because a large body of clinical data has suspected the involvement of the immune response, but has not yet dissected the causal relationship between the immune response and severe muscularization of arteries in the lungs.